The invention relates to an apparatus for manufacturing bags comprising a mandrel for shaping a band made from a packing material into a tube, a sealing device for dividing the tube into separate bags, and a rotatable conveying device for feeding the tube.
Apparatuses for manufacturing bags or bag packaging, in which a packing material band is shaped to form a tube, and the tube is drawn forward and divided cyclically by one bag length in each instance, are substantially divided into two types; namely, gripper feed machines and belt or roller feed machines. In gripper feed machines, the tube is fed by a bag length in each instance by a transverse sealing device which is moved in reciprocating or up-and-down motion, while the tools of the transverse sealing device simultaneously apply transverse seams to the tube and divide a bag. In these machines, the sealing time corresponds to the feed time. A disadvantage of this type of tube bag machine is that the end is shaped in a wedge-shaped manner by an exerted tension during the drawing forward of the tube, so that a formation of a base is impeded and, accordingly, the holding or volumetric capacity of the bag is not fully utilized.
In belt or roller feed machines, on the other hand, the tube is drawn forward by a bag length in a stepwise manner by a pair of conveying belts or rollers by frictional engagement, and the transverse sealing seams are applied by a stationary sealing device during every stoppage. In this type of tube bag machine, a clean standing base can be formed, but it has the disadvantage that the time for the transverse seam sealing and for the tube feed are cumulative, and the output of this type of machine is accordingly lower than that of the gripper feed machine.
Further, a tube bag machine is known from DE-OS No. 21 34 475 in which the tube feed is carried out by a reciprocated transverse sealing device as well as by conveying rollers or belts which are conveyed cyclically. In this tube bag machine, however, the transverse sealing device is moved in a reciprocating manner only a part of the length of the bag to be manufactured, and the remaining tube length for a bag to be manufactured is drawn forward with the aid of the conveying rollers or belts. In this known tube bag machine, it is very difficult to manufacture bags having the same length in each instance. Moreover, the time which is available for the transverse seam sealing is not fully used.